Path Tracing, Ambient Occlusion, and a Parser

24 Aug 2017

Release Notes

Rust crate to implement at least parts of the PBRT book's C++ code:

https://github.com/wahn/rs_pbrt

Current Rust documentation:

https://www.janwalter.org/doc/rust/pbrt/index.html

v0.2.0

Let's first show the latest image:

Cornell Box scene rendered via Rust version of PBRT using path
tracing (low settings)

This was rendered using path tracing. Since my last post a lot of things changed. First of all I started implementing a parser using a crate called pest. The parser isn't finished yet, but I provide some sample scenes which can be used and should render. The image above was for example rendered by the following command line ($ is the command prompt):

$ ./target/release/examples/pest_test -i assets/scenes/cornell_box.pbrt

Cloning the Repository

To compile the executable mentioned above you first need to clone the repository:

$ git clone https://github.com/wahn/rs_pbrt.git

Rustup

The easiest way to install Rust is rustup:

$ curl https://sh.rustup.rs -sSf | sh

I first started using some Rust features which require Rust nightly when I started working on the parser, but currently even the library (API) needs it:

$ rustup install nightly
$ rustup default nightly
info: using existing install for 'nightly-x86_64-unknown-linux-gnu'
info: default toolchain set to 'nightly-x86_64-unknown-linux-gnu'

  nightly-x86_64-unknown-linux-gnu unchanged - rustc 1.20.0-nightly

Compiling

After switching to the nightly version you should be able to compile:

$ cargo test --release
   Compiling pest v0.4.1
...
   Compiling image v0.15.0
...
    Finished release [optimized] target(s) in 113.58 secs
     Running target/release/deps/pbrt-e363c28050f255bc

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

   Doc-tests pbrt

running 16 tests
test src/lib.rs -  (line 166) ... ok
test src/lib.rs -  (line 24) ... ok
test src/lib.rs -  (line 204) ... ok
test src/lib.rs -  (line 112) ... ok
test src/lib.rs -  (line 241) ... ok
test src/lib.rs -  (line 277) ... ok
test src/lib.rs -  (line 301) ... ok
test src/lib.rs -  (line 319) ... ok
test src/lib.rs -  (line 373) ... ok
test src/lib.rs -  (line 344) ... ok
test src/lib.rs -  (line 412) ... ok
test src/lib.rs -  (line 462) ... ok
test src/lib.rs -  (line 53) ... ok
test src/lib.rs -  (line 551) ... ok
test src/lib.rs -  (line 596) ... ok
test src/lib.rs -  (line 84) ... ok

test result: ok. 16 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

Rendering

Now you are ready to render:

$ ./target/release/examples/pest_test -i assets/scenes/cornell_box.pbrt
...
Rendering finished
Converting image to RGB and computing final weighted pixel values
Writing image "pbrt.png" with bounds Bounds2 { p_min: Point2 { x: 0, y: 0 }, p_max: Point2 { x: 500, y: 500 } }
done.

This should take only a couple of seconds. Don't worry if your resulting image will look a lot more noisy. To render the exact same image as above you have to tweak some settings in the scene descrition file (cornell_box.pbrt):

Sampler "lowdiscrepancy" "integer pixelsamples" [512]
PixelFilter "gaussian" "float xwidth" [2.000000 ] "float ywidth" [2.000000 ]
Integrator "path"

Direct Lighting

To render without global illumination you can use the direct lighting integrator:

Integrator "directlighting" "integer maxdepth" [10]

Don't forget to use lower pixelsamples settings (maybe 8).

Cornell Box scene rendered with direct lighting

Ambient Occlusion

To render with ambient occlusion switch (again) the integrator:

Integrator "ambientocclusion"

Cornell Box scene rendered with ambient occlusion

Other Scenes

There are a couple of other scenes which can be rendered from the command line by parsing a scene description file, e.g. a teapot illuminated by an area light:

$ ./target/release/examples/pest_test -i assets/scenes/teapot-area-light.pbrt

Teapot scene rendered with direct·lighting

Variations of the Same Scene

From the time where I didn't have a parser there exists an executable which uses only the API (see also Wiki):

$ ./target/release/examples/pbrt_spheres_differentials_texfilt --help
Usage: ./target/release/examples/pbrt_spheres_differentials_texfilt [options]

Options:
    -h, --help          print this help menu
    -c, --checker       use procedural texture
    -i, --image         use image texture
    -n, --none          use no texture
    -m, --matte         use only matte materials
    -v, --version       print version number

Checker

Using a
procedural pattern on the floor.

Image

Using a
image file as texture on the floor.

No Texture

Matte
floor.

Matte

Matte only
materials.

Contribute

If you want to contribute to this project contact me via the email provided on the imprint page.